It is customary in the blueprint art to bind one edge of a set of blueprints with a strip of folded paper. Such paper binders may be formed by cutting a desired shape from a flat sheet of paper or by cutting a desired length from an elongate roll of paper to provide a paper web. The folding operation has been traditionally performed manually by making at least three longitudinal folds in the paper web to form a generally U-shaped paper binder of double thickness. The paper binder is then stapled or otherwise attached to one edge of a stack of blueprints or the like. Manual folding of the paper web, however, is inefficient and time consuming.
U.S. Pat. No. 4,089,514 (incorporated herein by reference) to Skipworth discloses apparatus for folding paper in a manner suitable for use as a paper binder for blueprints. The apparatus comprises folding channels of complex shape and design. The apparatus also includes drive rolls and creasing rolls. The folding channels and rollers are relatively expensive and difficult to manufacture.